A wide variety of hardware brackets, clamps and fasteners have been used in the construction trades for joining and securing timbers and other structural members together in different arrangements. A principal problem area is the joinder of shelf boards or like structural members, and a typical solution has been to apply one or more straight or angle straps across the juncture of the two boards. A number of corner brackets or devices have been proposed for joining the corner frame pieces of door or window sash, as disclosed in U.S. Pat. Nos. 1,045,815; 1,591,869; 1,820,206; 2,039,125 and 4,039,137, but the prior art does not teach a simple, one-piece bracket applied at the inside corner of two shelf boards or like structural members and engageable with opposed surfaces thereof.